Switch operated tone control circuitry and amplifier for musical instruments

ABSTRACT

The tone control circuit is particularly suited for an amplifier designed primarily for musical tone signals, for example, those generated by an electric guitar. Within the ready and instant control of the instrument player or performer is a switch actuator, such as a foot switch, by means of which there may be selectively connected in and out of the amplifier circuit a frequency-discriminating circuit or network. The network discriminates in favor of a narrow band of frequencies. By operating the foot switch in synchronism with his playing, the performer can create novel effects under his continuous control. The frequency-discriminating network is integrated into the conventional treble and bass manual controls on the amplifier so as to make double use of circuit components and create novel musical response.

United States Patent [72] Inventors Fred H. Neubauer Pacific Palisades; Sava W. Jacobson, Northridge, both of, Calif. [21] Appl.No.- 631,008 [22] Filed Apr. 14, 1967 [45] Patented July 6, 1 971 [73] Assignee Warwick Electronics Inc.

Chicago, I11. I

[54] SWITCH OPERATED TONE CONTROL I CIRCUITRY AND AMPLIFIER FOR MUSICAL INSTRUMENTS 9 Claims, 31 Dra ing Figs. [52] US. Cl 84/1-24, 84/ 1.19, 84/D1G. 7, 84/DIG. 9 [51] Int. Cl G101! 1/02 [50] Field of Search. 84/124, 1.25,1.1 1.01, 1.1 1,1.14, 1.19, 1.21, 1.27

[56] References Cited UNITED STATES PATENTS 3,178,501 4/1965 Evans 84/l.l6 3,217,079 11/1965 Murrell 84/U 3,255,296 6/1966 Peterson... 84/ 1.24 3,288,909 11/1966' Volodin 84/].25

2,698,360 12/1954 .Seybold 84/1 .27 X

3,045,522 7/1962 Markowitz et al 84/127 3,240,859 3/1966 Rowe 84/].25

3,278,672 10/1966 Grodinsky et al.... 84/127 OTHER REFERENCES ALTERNATlNG-CURRENT CIRCUITS, by Russell M. Kerchner and George F. Corcoran, (1958) pp. 468, 4 69 Primary Examiner-Milton O. l-lirshfield Assistant Examiner-Stanley J. Witkowski Attorney-Warren T. Jessup 'former is a switch actuator, such as a foot switch, by means of which there may be selectively connected in and out of the amplifier circuit a frequency-discriminating circuit or network. The network discriminates in favor of a narrow band of ij-equencies. By operating the foot switch in synchronism with his playing, the performer can create novel effects under his continuous control. The frequency-discriminating network is integrated into the conventional treble and bass manual controls on the amplifier so as to make double use of circuit components and create novel musical response.

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52258 3% Bu o W T T m1 mw GZZSLU 32x02 ATTORNEY SWITCH OPERATED TONE CONTROL ClIRCUITRY AND AMPLIFIER FOR MUSICAL INSTRUMENTS BACKGROUND OF THE INVENTION Tone control circuits are well known in the field of musical amplifiers. Refined versions of said circuits are to be found, for example, in the formant circuits of electronic organs. By actuating appropriate formant tabs, the organist is able to devise a wide variety of tonal effects, by selecting those circuits which give desired timbre to the tone sounded. Such tabs, although located within easy access of the organist, are not playing keys, in that the organist does not constantly rest his hands upon and continually run back and forth over the tabs in the manner of the playing manual of the organ. The tabs are left in actuated position for several and usually many bars of the music.

With the advent of electronic amplification to many forms of musical instruments which were previously purely acoustic,

the manner of placement of tone controls became of serious concern, because the amplifier and control panel for the instrument, unlike the case of an organ, is usually spaced some distance from the instrument and the performer.

SUMMARY OF THE INVENTION A tone control circuit is incorporated into the amplifier of a hand-held musical instrument. This circuit discriminates significantly in favor of a given narrow band of frequencies. It is selectively enabled or disabled, i.e., placed in operative association with the amplifier or otherwise, by means of a control member which is under the ready and constant manipulation of the instrument player, for example, a foot pedal on which a guitar player may at will operate the control member with his foot. In this way the guitarist may quickly and with great rapidity enable and disable the frequency selective circuit. If desired, this may be done in tempo with the playing of the music, to create strikingly novel musical effects.

Another control, which is preferably placed on the panel of the amplifier itself, enables the performer to select one of a number of different frequency bands which are to be preferred by the foot-controlled circuit.

The present invention also involves the incorporation of the frequency selective circuit into the conventional treble and bass controls to make multiple use of circuit components and create a desirable frequency response in the amplifier.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a complete amplifier for a hand-held musical instrument, such as a guitar;

FIG. 2 is a circuit diagram of that portion of the amplifier involving the circuit of the present invention;

FIG. 3 are frequency response curves illustrating operation of the invention;

FIG. 4 is a drawing of an alternative form of control for the circuit of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT FIG. 1 is a block diagram of an amplifier, specifically an amplifier for hand-held musical instruments, such as a guitar. Blocks l2, 2, and 16 represent, respectively, different input channels to which the musical instruments represented by the tone generator symbols 18 may be plugged into. Block 12, for example, represents a normal channel; block 2 a brilliant channel, i.e., one tending to favor somewhat the higher frequency components of the tone; and block 16 represents a bass channel.

Channels 12 and 2 may be fed to a reverberation circuit 20, thence through a tremolo circuit 22, and thence through a peak limiter 24 and amplifier 26 to a loudspeaker 28. The bass channel output is sent direct to the amplifier 26 through peak limiter 24.

The circuit of the present invention is incorporated in the brilliant channel 2, as will now be described with reference to FIG. 2.

In FIG. 2, 30 represents parallel input jacks by means of which two hand-held instruments, such as guitars, may be simultaneously fed into the amplifier. Tone signal applied at 30 is first amplified in a two-stage amplifier represented by transistors 34 and 36. The tone is then applied across a treble potentiometer 38 and a bass potentiometer 40, connected in series through a resistor 42. FIG. 2 being the brilliant channel of the amplifier, the capacitor 44 tends to give some preference to the higher harmonics in the tone.

The slider 46 of the treble potentiometer 38 is connected to capacitors 48, 50, and 52, any one of which may be selectively placed in series with the slider 46 by the triple-throw switch 54. In the position shown, switch 54 places the capacitor 48 in the circuit.

Tone signal passing through capacitor 48 is applied through capacitors 56 and 58 across a volume control potentiometer 60 and back to the ground connection 62. Output from the brilliant channel FIG. 2 is taken from the volume control slider 64 and applied to the next stage. In the example of FIG. I this would be the block 20.

An intermediate tone path is taken from the junction point 66 between the resistors 42 and 40, through an inductor 68 and resistor 70, to the junction point 71 between the capacitors 56 and 58. A manually operable switch 72 is connected between the points 74 and 76. This switch is preferably located on the panel of the amplifierfiSwitch 72 is paralleled by switch contacts 78 controlled by a relay 80, energized from a pedal-controlled switch 82, which completes the circuit to ground from the voltage source through a resistor 92 and the relay coil 80. Either or both the switches 72 and 78 may be replaced by a light-dependent resistor (LDR) with an as sociated light source under the control of the performer. When the performer illuminates the LDR, the circuit is closed; when he darkens the LDR, the circuit is open. In FIG. 4 the performer or guitarist 101 controls with his foot a light source I02 whose beam 103 is directed onto a LDR 72A. FIG. 4 thus illustrates the replacement of the switch 72 of FIG. 2 with a LDR 72A as explained above. By suitable foot control of the light source I02, the performer 101 may either turn the light beam completely off or completely on, or may modulate this intensity with consequent modulation of the resistance of the LDR 72A.

A series-connected capacitor 84 and resistor 86 are connected in shunt across the bass potentiometer 40, and the junction point between these two is connected to the bass slider 88 of the potentiometer 40.

OPERATION The switch 78 is normally biased to open condition and must be held in closed condition by the performer. In the case of the switch 78, this involves keeping the coil 80 energized, which is done by keeping depressed the pedal that closes the switch 82. When the pedal is released, the switch 82 opens, deenergizing the relay and opening the contact 78.

With both switches 72/78 open, the frequency response is as shown at curve in FIG. 3, which represents output amplitude as ordinate and frequency as abscissa, for a given setting of tone controls 46 and 88. In the lowv and middle frequency ranges, the response, as shown at 100, is that of a typical audioamplifier. Several of the components, primarily 44, 68, 70 and 56 contribute to produce a rising high frequency response, as shown.

With either of the switches 72/78 closed, the pass circuit represents essentially an L-section capacitance/inductance,

. high pass filter network, operating above critical damping, and

RC circuit, taking the output from point 76 and applying it through the coupling capacitor 58 to the output volume resistor 60. As the frequency increases, the resonance peak 104 is passed and the amplitude drops ofi, as shown at 106. lt then begins to rise steadily as the inductor 68 increases in impedance and the capacitor 56 decreases in impedance.

When the switch 54 is actuated to insert the capacitor 50in lieu of 48, the resonant frequency is lower, and, hence, the peak 108 moves down the frequency scale. Similarly, when capacitor 52 is switched into the circuit, the resonant peak appears at 110.

With normal playing, the amplifier of H0. 2 responds along the curve 100. By depressing the pedal 82, on which his foot continually rests, the performer can instantly cause the response to peak as shown, for example, at 104. Then by simply lifting his foot, or releasing the pedal, the response reverts to the curve 100. This instant switching between response curves can be done in tempo with the rhythm of the music to produce many varied effects.

Capacitors 48, 50, 52 may be replaced by a single, variable capacitor controllable by the performer. The resonant peak 104 (108,110) then becomes continuously adjustable across the frequency spectrum. Such adjustment may also be by pedal control, if desired.

The treble control 46 and the bass control 88 also make use of some of the same components as are employed in the selective frequency control heretofore described. Consider first the reaction of the circuit with the switches 72/78 open. When the slider 88 is in its lowermost position, the resistor 86 is short circuited and in effect replaced by the capacitor 84. The capacitor 84 is of such value as to represent a considerable impedance for lower frequencies, but a much less impedance for the higher frequencies of the tone. Thus there is considerable bass tone developed across capacitor 84, which is fed from the point 66 through the components 68, 70, and 58 to the output resistor 60. This is the maximum bass position.

When the slider 88 is in its uppermost position, there is a short circuit across capacitor 84. Since resistor 86 is very small, very little signal is developed at point 66. Thus the principal path is through 48 and 56, which represent high impedance to bass tones. This is the position of minimum bass amplification or tone.

Considering the treble control, the capacitors 48, 50, 52 and 58 are relatively large compared to capacitor 56. Therefore, as a first approximation, they have little effect on treble tones. When the slider 46 is uppermost, there is maximum transmission of the treble tones, which pass through the capacitors 48, 56, and 58 to the output. As noted, the capacitor 56 is relatively small and, therefore, gives significantly greater pass preference to the treble tone signals.

When the slider 46 is in its lower position, the tone signals developed across the resistor 38 are no longer applied to the output and, hence, the only signals that are applied are those developed across the resistors 40, 42, which are applied to the capacitors 48, 56, and 58.

The inductor 68 has the function of tending to block the treble tone signals, even those developed across the network 40, 84, and 86, so that the significant treble tones which reach the output do so from the slider 46. The preference of the path 48, 56 for high frequency or treble tone signals is further accentuated by the function of the inductor 68, serving as a relatively high impedance load connected from the point 71 to ground through the bass circuit components 40, 84 and 86. The inductor 68 thus has the double function of presenting a load at point 71 which favors the passage of treble tones through the circuit 48, 56, and of representing a series blocking impedance which blocks the passage of treble tones from the point 66 to the output point 71.

With either of the switches 72, 78 closed, the components 70, 56 represent, as noted hereinbefore, simply a parallel connected RC circuit coupling the output point 76 to the output volume control resistor 60. The function of the components discussed immediately above in connection with the treble potentiometer 38 and the bass potentiometer 40, is substantially the same as described hereinbefore. The significant output point in this case is simply the point 76 rather than the point 71, because of the closing of the switch 72 (or 78).

A satisfactory circuit constructed according to FIG. 2 has the following parameters.

Transistors 34 and 36 2N900A Capacitor 44 microfarads Whereas the present invention has been shown and described herein in what is conceived to be the best mode contemplated, it is recognized that departures may be made therefrom within the scope of the invention, which is, therefore, not to be limited to the details disclosed herein, but is to be afforded the full scope of the invention as hereinafter claimed.

What we claim is: 1. Tone control circuit for a hand-held musical instrument amplifier, comprising:

an audiofrequency pass circuit comprising an L-section capacitance/inductance high pass filter network operating above critical damping, and having an input adapted to be fed from the electronic output of a hand-held musical instrument and an output adapted to feed an electroacoustic transducer, said circuit being effective to give a greater pass preference to a certain narrow band of frequencies therein, and v means readily operable by the player of the musical instrument for selectively enabling and disabling said pass circuit, and being biased to a position not giving preference to said band, whereby the tone control circuit may selectively prefer or not prefersaid band of frequencies at the ready will of the player, but requiring the player to maintain the operable means in operated position for so long as he desires said pass preference to be given by. the pass circuit. 2. Tone control circuit for a hand-held musical instrument amplifier, comprising:

an audiofrequency pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument, and an output adapted to feed an electroacoustic transducer,

said circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the circuit, over other frequencies therein, and

a player-operable on/off switch, readily operable by the player of the musical instrument, for selectively enabling and disabling said circuit, whereby the tone control circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player, and pedaloperated means readily operable by the foot of the player for operating said switch. 3. Tone control circuit for a hand-held musical instrument amplifier comprising:

an audiofrequency pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument, and an output adapted to feed an electroacoustic transducer, said circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the circuit, over other frequencies therein, and a player-operable on/off switch including a light dependent resistor readily operable by the player of the musical instrument, for selectively enabling and disabling said circuit, whereby the tone control circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player. 4. Tone control circuit for a hand-held musical instrument amplifier, comprising:

an audiofrequency pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument, and an output adapted to feed an electroacoustic transducer, said circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the circuit, over other frequencies therein, and a player-operable on/off switch, readily operable by the player of the musical instrument, for selectively enabling and disabling said circuit, whereby the tone control circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player, said switch comprising: the contacts of a relay also having a coil, a conductor connected to said coil, a second switch connected to said conductor for selectively energizing and deenergizing said coil, and pedal means for actuating said second switch. 5. Tone control circuit for a hand-held musical instrument amplifier, comprising:

an audiofrequency pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument and an output adapted to feed an electroacoustic transducer, said pass circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the pass circuit, over other frequencies therein, said pass circuit comprising an L-section capacitance/inductance high pass filter network operating above critical damping, the capacitance of said network being connected to said input and the inductance of said network being connected across said output, and means readily operable by the player of the musical instrument for selectively enabling and disabling said pass circuit and including switch means connected in series with said inductance, whereby the tone control circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player. 6. Tone control circuit for a hand-held musical instrument amplifier, comprising:

an audiofrequency pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument and an output adapted to feed an electroacoustic transducer,

said pass circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the pass circuit, over other frequencies therein, said pass circuit comprising an L-section capacitance/inductance high pass filter network operating above critical dampin said capacitance comprising a plurality of capacitors, a multithrow switch for connecting one of said capacitors into said network, and

means readily operably by the player of the musical instrument for selectively enabling and disabling said pass circuit,

whereby the tone circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player.

7. Tone control circuit for a hand-held musical instrument amplifier, comprising:

an audiofrequency resonant pass circuit having an input adapted to be fed from the electronic output of a handheld musical instrument and an output adapted to feed an electroacoustic transducer, said resonant pass circuit being efi'ective to give greater pass preference to a certain narrow band of frequencies within the range of the pass circuit, over other frequencies therein,

a pair of adjustable resistance means connected in series across said input,

circuit means connecting one terminal of said resonant pass circuit to one of said resistance means,

circuit means connecting the other terminal of said resonant pass circuit to the other of said resistance means, and

means readily operable by the player of the musical instrument for selectively enabling and disabling said pass circuit,

whereby the tone signal circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player.

8. Tone control circuit for a hand-held musical instrument amplifier, comprising:

an audiofrequency pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument and an output adapted to feed an electroacoustic transducer,

said pass circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the pass circuit, over other frequencies therein,

said pass circuit comprising an L-section capacitance/inductance high pass filter network operating above critical damping,

said capacitance of said network being connected across said output, and

means readily operable by the player of the musical instrument for selectively enabling and disabling said pass circuit and including switch means series connected in circuit between said capacitance and said inductance,

a second capacitance connected between said first-mentioned capacitance and said output,

and a resistor connected from the junction point between said inductance and said switch means to said output.

9. Tone control circuit for a hand-held musical instrument amplifier, comprising:

an audiofrequency pass circuit having an input adapted to be fed from the electronicoutput of a hand-held musical instrument and an output adapted to feed an electroacoustic transducer,

said circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the circuit, over other frequencies therein,

a player-operable on/off switch readily operable by the player of the musical instrument for selectively enabling and disabling said pass circuit, and being biased to a position not giving preference to said band, and

a readily operable foot pedal for actuating said switch,

whereby the tone control circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player, but requiring the player to maintain said switch in operated position for so long as he desires said preference to be given by the pass circuit. 

1. Tone control circuit for a hand-held musical instrument amplifier, comprising: an audiofrequency pass circuit comprising an L-section capacitance/inductance high pass filter network operating above critical damping, and having an input adapted to be fed from the electronic output of a hand-held musical instrument and an output adapted to feed an electroacoustic transducer, said circuit being effective to give a greater pass preference to a certain narrow band of frequencies therein, and means readily operable by the player of the musical instrument for selectively enabling and disabling said pass circuit, and being biased to a position not giving preference to said band, whereby the tone control circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player, but requiring the player to maintain the operable means in operated position for so long as he desires said pass preference To be given by the pass circuit.
 2. Tone control circuit for a hand-held musical instrument amplifier, comprising: an audiofrequency pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument, and an output adapted to feed an electroacoustic transducer, said circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the circuit, over other frequencies therein, and a player-operable on/off switch, readily operable by the player of the musical instrument, for selectively enabling and disabling said circuit, whereby the tone control circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player, and pedal-operated means readily operable by the foot of the player for operating said switch.
 3. Tone control circuit for a hand-held musical instrument amplifier comprising: an audiofrequency pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument, and an output adapted to feed an electroacoustic transducer, said circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the circuit, over other frequencies therein, and a player-operable on/off switch including a light dependent resistor readily operable by the player of the musical instrument, for selectively enabling and disabling said circuit, whereby the tone control circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player.
 4. Tone control circuit for a hand-held musical instrument amplifier, comprising: an audiofrequency pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument, and an output adapted to feed an electroacoustic transducer, said circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the circuit, over other frequencies therein, and a player-operable on/off switch, readily operable by the player of the musical instrument, for selectively enabling and disabling said circuit, whereby the tone control circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player, said switch comprising: the contacts of a relay also having a coil, a conductor connected to said coil, a second switch connected to said conductor for selectively energizing and deenergizing said coil, and pedal means for actuating said second switch.
 5. Tone control circuit for a hand-held musical instrument amplifier, comprising: an audiofrequency pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument and an output adapted to feed an electroacoustic transducer, said pass circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the pass circuit, over other frequencies therein, said pass circuit comprising an L-section capacitance/inductance high pass filter network operating above critical damping, the capacitance of said network being connected to said input and the inductance of said network being connected across said output, and means readily operable by the player of the musical instrument for selectively enabling and disabling said pass circuit and including switch means connected in series with said inductance, whereby the tone control circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player.
 6. Tone control circuit for a hand-held musical instrument amplifier, comprising: an audiofrequency pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument and an output adapted to feed an electroacoustic transducer, said pass circuit being effective to give greater pass preference to a cerTain narrow band of frequencies within the range of the pass circuit, over other frequencies therein, said pass circuit comprising an L-section capacitance/inductance high pass filter network operating above critical damping, said capacitance comprising a plurality of capacitors, a multithrow switch for connecting one of said capacitors into said network, and means readily operably by the player of the musical instrument for selectively enabling and disabling said pass circuit, whereby the tone circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player.
 7. Tone control circuit for a hand-held musical instrument amplifier, comprising: an audiofrequency resonant pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument and an output adapted to feed an electroacoustic transducer, said resonant pass circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the pass circuit, over other frequencies therein, a pair of adjustable resistance means connected in series across said input, circuit means connecting one terminal of said resonant pass circuit to one of said resistance means, circuit means connecting the other terminal of said resonant pass circuit to the other of said resistance means, and means readily operable by the player of the musical instrument for selectively enabling and disabling said pass circuit, whereby the tone signal circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player.
 8. Tone control circuit for a hand-held musical instrument amplifier, comprising: an audiofrequency pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument and an output adapted to feed an electroacoustic transducer, said pass circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the pass circuit, over other frequencies therein, said pass circuit comprising an L-section capacitance/inductance high pass filter network operating above critical damping, said capacitance of said network being connected across said output, and means readily operable by the player of the musical instrument for selectively enabling and disabling said pass circuit and including switch means series connected in circuit between said capacitance and said inductance, a second capacitance connected between said first-mentioned capacitance and said output, and a resistor connected from the junction point between said inductance and said switch means to said output.
 9. Tone control circuit for a hand-held musical instrument amplifier, comprising: an audiofrequency pass circuit having an input adapted to be fed from the electronic output of a hand-held musical instrument and an output adapted to feed an electroacoustic transducer, said circuit being effective to give greater pass preference to a certain narrow band of frequencies within the range of the circuit, over other frequencies therein, a player-operable on/off switch readily operable by the player of the musical instrument for selectively enabling and disabling said pass circuit, and being biased to a position not giving preference to said band, and a readily operable foot pedal for actuating said switch, whereby the tone control circuit may selectively prefer or not prefer said band of frequencies at the ready will of the player, but requiring the player to maintain said switch in operated position for so long as he desires said preference to be given by the pass circuit. 